LTC3128
3A Monolithic Buck-Boost
Supercapacitor Charger and
Balancer with Accurate Input Current Limit
FEATURES DESCRIPTION
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2% Accurate Average Input Current Limit
The LTC 3128 is a highly efficient, buck-boost DC/DC
Programmable Up to 3A
supercapacitor charger. It operates efficiently from input
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Programmable Maximum Capacitor Voltage Limit
voltages above, below or equal to the output voltage. The
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Active Charge Balancing for Fast Charging of
LTC3128 incorporates accurate programmable average
Unmatched Capacitors
input current limit, active charge balancing and program-
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Charges Single or Stacked Capacitors
mable maximum capacitor voltage. This combination of
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V Range: 1.73V to 5.5V
features makes the LTC3128 ideal for safely charging and
IN
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V Range: 1.8V to 5.5V
protecting large capacitors in backup power systems. The
OUT
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<2A Quiescent Current from V When Charged
input current limit and maximum capacitor voltage are each
OUT
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Output Disconnect in Shutdown: <1A I Shutdown
programmed using a single resistor. Average input current
Q
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Power-Good Comparator
is accurately controlled over a 0.5A to 3A programmable
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Power Failure Indicator
range while the individual maximum capacitor voltage can
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Thermally Enhanced 20-Lead (4mm 5mm 0.75mm)
be set from 1.8V to 3.0V.
QFN and 24-Lead TSSOP Packages
Other features of the LTC3128 include <2A quiescent
current from V in Burst Mode operation, accurate
OUT
APPLICATIONS
power-good and power failure indicators, and thermal
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Supercapacitor Based Backup Power
overload protection. The LTC3128 is offered in low profile,
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Memory Backup
thermally enhanced 20-Lead 4mm 5mm 0.75mm QFN
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Servers, RAID, RF Systems
and 24-Lead TSSOP packages.
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Industrial, Communications, Computing
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
and PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
TYPICAL APPLICATION
Wide V (3A Programmed Input Current) to 4.2V
IN
Stacked Output Capacitors Charging Waveform
3.3H
SW1 SW2
V = 4.2V
OUT
V
RSENP
OUTP
V
V OUT
1.7V TO 5.5V RSENS OUTS
C1a
2.0V/DIV
1.87M
UP TO 3.0A
LTC3128 940mF
V
IN
C1
MID MID
RUN C1b
2.0V/DIV
940mF
PFI
FB I
IN
PFO
2.0A/DIV
10F
PGOOD
MAXV PROG
10F
GND I
LOAD
2.0A/DIV
127k 470pF 3.57k 301k
3128 TA01b
3128 TA01 2 SECONDS/DIV
C1: Murata DMF3Z5R5H474M3DTA0
3128f
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For more information www.linear.com/LTC3128LTC3128
ABSOLUTE MAXIMUM RATINGS
(Note 1)
V , RSENP, V , MID Voltage .................. 0.3V to 6V PROG, MAXV, FB, PFI Voltage ..................... 0.3V to 6V
IN OUTP
RSENS, V Voltage ................................. 0.3V to 6V PGOOD, PFO DC Current ........................................15mA
OUTS
RSENS DC Current ....................................................4A Operating Junction Temperature Range
SW1, SW2 DC Voltage ................................. 0.3V to 6V (Notes 2, 4) ............................................ 40C to 125C
SW1, SW2 Pulsed (<100ns) Voltage .............1.0V to 7V Storage Temperature Range .................. 65C to 150C
PGOOD, PFO, RUN Voltage .......................... 0.3V to 6V Lead Temperature (Soldering, 10 sec)
FE Only .............................................................300C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
SW1 1 24 SW2
GND 2 23 SW2
20 19 18 17 GND 3 22 NC
SW1 4 21 V
OUTP
SW1 1 16 V
OUTP
RSENP 5 20 V
RSENP 2 15 V OUTP
OUTP
RSENS 3 14 V RSENS 6 25 19 V
OUTS
OUTS
21
GND
GND
RUN 4 13 MID
RUN 7 18 MID
PROG 5 12 PGOOD
PROG 8 17 PGOOD
NC 6 11 FB
NC 9 16 FB
7 8 9 10 NC 10 15 MAXV
V 11 14 PFI
IN
GND 12 13 PFO
UFD PACKAGE
20-LEAD (4mm 5mm) PLASTIC QFN
FE PACKAGE
T = 125C, = 43C/W
JMAX JA
24-LEAD PLASTIC TSSOP
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB (NOTE 5)
T = 125C, = 38C/W
JMAX JA
EXPOSED PAD (PIN 25) SHOULD BE SOLDERED TO PCB (NOTE 5)
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3128EUFD#PBF LTC3128EUFD#TRPBF 3128 20-Lead (4mm 5mm) Plastic QFN 40C to 125C
LTC3128IUFD#PBF LTC3128IUFD#TRPBF 3128 40C to 125C
20-Lead (4mm 5mm) Plastic QFN
LTC3128EFE#PBF LTC3128EFE#TRPBF LTC3128FE 24-Lead Plastic TSSOP 40C to 125C
LTC3128IFE#PBF LTC3128IFE#TRPBF LTC3128FE 24-Lead Plastic TSSOP 40C to 125C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: